Thanks for the help in advance; first time posting here.
I’m curious what the most appropriate single word is to describe a 9 year time span, or a 9 year anniversary. A search on Google didn’t turn up much, but it did help me find this information in the Wiki page for “decade”: “…Other words for spans of years also come from Latin: biennium (2 years), triennium (3 years), quadrennium (4 years), lustrum (5 years)“.
Following this pattern, the most appropriate form of the word I could come up with is novemnium, seeing as novem is Latin for 9. Is this the correct structure/spelling, or are there better alternatives to this problem?
The noun form of user’s answer (novennial), and I believe you are looking for a noun, is novennium
(rare) A nine-year period or cycle.
Also see enneatic:
Occurring once in every nine times, days, years, etc.; every ninth.
And finally, enneaeteric
Containing or consisting of nine years: as, an enneaeteric period.